(revised 11/29/01 to correct CO2 units factor)
(Revised 7 Mar 06 changed default downstream pressure to 14.7)

### For gas flow through an orifice the Lohms Laws are:

Sonic Flow -- P1/P2 > 1.9 Sub-Sonic Flow -- P1/P2 < 1.9
Important Nomenclature:

 K = Gas Units Constant fT = Temprature Correction Factor P1 = Upstream absolute pressure

 P2 = Downstream Absolute pressure Q = Gas flow DeltaP = P1 -P2

Step 1: Enter temprature of Gas:
 degrees F C

Temp Correction factor:
Step 2:

Select a Gas:
 Air Argon CO CO2 Ethane Freon-12 He H2 N2 N2O Nat. Gas Neon O2 SO2
Step 3:

Select a Pressure Unit:
Psia
Bar
kPa
kg/(sq. cm)
ft H2O
mmHg
Step 4:

Select a Flow Unit:
Standard Liters per Minute
Standard milliLiters per Minute
Standard cu. Meter per Minute
Standard cu. inches per Minute
Standard cu. feet per Minute
Automatically calculated from the gas and unit information entered, the units factor (K) is

Step 5:

Enter data into the input area of one of the scenarios below, and click the calculate button in that box. Results will appear in the answer area.

A. If you know the pressure and flow and need to find Lohms:

Inputs:

 Upstream: Downstream: Flowrate:

 Lohms =

B. If you know pressure and Lohms and need to find flow:

Inputs:

 Upstream: Downstream: Lohms:

 Flowrate =

C. If you know Lohms and Flow and need to find Upstream pressure:

Inputs:

 Lohms: Downstream: Flowrate: